1. Field of the Invention
The present invention relates to a measuring apparatus for measuring relative parallel displacement/inclination of the measured portion to the measuring reference portion in the precision measuring technology field, and an antenna system equipped with this measuring apparatus to correct the pointing error.
2. Description of the Related Art
In the field of the radio astronomy, for example, recently the request for the observation of the radio wave with a higher frequency from a millimeter wave to a submillimeter wave is being increased. If the observation of the radio-wave celestial sphere is carried out by the high frequency, the higher precision is required in the directivity tracking of the reflecting mirror surface of the telescope and the beam. In contrast, the larger aperture size of the telescope is accelerated in order to increase the observation efficiency, and also it is required to make all weather observation at day and night. Since the aperture size is increased, the self-weight deformation of the telescope is increased, otherwise the thermal deformation due to the solar radiation or the deformation due to the wind pressure is increased. Therefore, it is difficult to get the high directivity tracking precision. In order to satisfy the request for such high directivity tracking precision, the technology for measuring/correcting the pointing error of the reflecting mirror of the telescope in real time is needed.
FIG. 6 is a configurative view showing an antenna angle sensing system shown in the Unexamined Japanese Patent Application Publication No. Hei 3-3402, for example, in the prior art. In FIG. 6, 1 is a main reflecting mirror, 2 is an antenna pedestal, and 3 is an AZ angle sensor of the antenna, which is fixed to the antenna pedestal 2. Also, 4 is an EL angle sensor of the antenna, 5 is an EL angle sensor that is the same type as the EL angle sensor 4 or a mount having only a case that is the same as the EL angle sensor. Also, 6 is a light beam generator and two light beam generators 6 are provided on the AZ angle sensor 3, and 7 is an AZ-axis optical position sensor provided on the EL angle sensors 4 and 5 respectively. The beam emitted from the light beam generator 6 is irradiated onto the AZ-axis optical position sensor 7. Also, 8 is a light beam generator that is provided on the EL angle sensors 4 and 5 respectively, and 9 is an EL-axis optical position sensor that is provided on the AZ angle sensor 3. The beam emitted from the light beam generator 8 is irradiated onto the EL-axis optical position sensor 9. The AZ-axis optical position sensor 7 and the EL-axis optical position sensor 9 are constructed by a two-split photo diode, and are arranged to sense the beam deviation only in the Y-axis direction.
Next, an operation will be explained hereunder. If the antenna pedestal 2 is deformed, the twist deformation upon the axis and the parallel deformation are generated. In the system shown in FIG. 6, two sets of the light beam generators 6 and the AZ-axis optical position sensors 7 are provided for the AZ axis, and two sets of the light beam generators 8 and the EL-axis optical position sensors 9 provided for the EL axis.
An amount of twist in the AZ axis is calculated based on the difference between outputs of two sets of the AZ-axis optical position sensors 7, and also an amount of twist in the EL axis is calculated based on the difference between a sum of outputs of two sets of the EL-axis optical position sensors 9 and a sum of outputs of two sets of the AZ-axis optical position sensors 7. The direction of the true antenna directivity is calculated by adding/subtracting respective amounts of twist of the axes, which are sensed in this manner, to/from angle signals that are sensed by the EL angle sensors 4, 5 and the AZ angle sensor 3 respectively.
Since the antenna angle sensing system in the prior art is constructed as above, the optical position sensors and the light beam generators must be arranged on the EL angle sensors and the AZ angle sensor. Therefore, there was such a problem that the arrangement of these devices puts the restriction on the antenna structure. Also, the employed sensors are the optical position sensor that senses the light beam. Therefore, there was another problem such that there is such a restriction that the marker for indicating the displacement of the measured site must be constructed by the high-output light beam generator. In addition, in the antenna angle sensing system in the prior art, the outputs of the angle sensors in respective axes are corrected based on the true directivity that was sensed. In this case, particularly the pointing error at the high frequency cannot be corrected by correcting only the outputs of the angle sensors, and thus there was still another problem such that the high antenna directivity tracking precision cannot be achieved.
The present invention is made to overcome the above-problem, and it is an object of the present invention to provide a parallel displacement/inclination measuring apparatus capable of measuring a parallel displacement and an inclination of the measured portion with the small restriction on arrangement of measuring devices and an antenna system for correcting the antenna pointing error by using this parallel displacement/inclination measuring apparatus.
A parallel displacement/inclination measuring apparatus according to the invention set forth in Aspect 1 comprises a first marker for indicating a position provided to a measuring reference portion; a first image sensor provided to a measured portion to oppose to the first marker; a second marker for indicating a position provided to the measured portion; a second image sensor provided to the measuring reference portion to oppose to the second marker; a position calculating portion for calculating positions of the first marker and the second marker, which are picked up by the first image sensor and the second image sensor; and a displacement/inclination calculating portion for calculating a parallel displacement and an inclination of the measured portion, based on the positions of the first marker and the second marker calculated by the position calculating portion.
An antenna system according to the invention set forth in Aspect 2 comprises an antenna pedestal for supporting an elevation angle driving axis of an antenna; a first marker for indicating a position provided to a top portion of the antenna pedestal; a first image sensor provided to a bottom portion of the antenna pedestal to oppose to the first marker; a second marker for indicating a position provided to the bottom portion of the antenna pedestal; a second image sensor provided to the top portion of the antenna pedestal to oppose to the second marker; a position calculating portion for calculating positions of the first marker and the second marker, which are picked up by the first image sensor and the second image sensor; and a displacement/inclination calculating portion for calculating a parallel displacement and an inclination of the top portion of the antenna pedestal, based on the positions of the first marker and the second marker calculated by the position calculating portion.
An antenna system according to the invention set forth in Aspect 3 comprises an antenna pedestal for supporting an elevation angle driving axis of an antenna; first markers for indicating positions provided to right and left portions of a top portion of the antenna pedestal respectively; first image sensors provided to right and left portions of a bottom portion of the antenna pedestal respectively to oppose to the first markers; second markers for indicating positions provided to right and left portions of the bottom portion of the antenna pedestal respectively; second image sensors provided to right and left portions of the top portion of the antenna pedestal respectively to oppose to the second markers; a position calculating portion for calculating positions of the first markers and the second markers, which are picked up by the first image sensors and the second image sensors; a displacement/inclination calculating portion for calculating parallel displacements and inclinations of the right and left portions of the top portion of the antenna pedestal, based on the positions of the first markers and the second markers calculated by the position calculating portion; and a pointing error calculating portion for calculating an antenna pointing error based on the parallel displacements and the inclinations of the right and left portions of the top portion of the antenna pedestal calculated by the displacement/inclination calculating portion.
In the antenna system according to the invention set forth in Aspect 3, the antenna system according to the invention set forth in Aspect 4 further comprises an antenna driving portion for driving the antenna on an azimuth angle or elevation angle axis based on the antenna pointing error calculated by the pointing error calculating portion to correct a direction of an antenna directivity.
In the antenna system according to the invention set forth in Aspect 3, the antenna system according to the invention set forth in Aspect 5 further comprises a subreflector driving portion for driving a subreflector based on the antenna pointing error calculated by the pointing error calculating portion to correct a direction of an antenna directivity.
In the antenna system according to the invention set forth in Aspect 3, the antenna system according to the invention set forth in Aspect 6 further comprises a high-speed driven mirror driving portion for driving a high-speed driven mirror based on the antenna pointing error calculated by the pointing error calculating portion to correct a direction of an antenna directivity.